JPH035104B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a system for transmitting a ringing signal to a subscriber's telephone in a telephone exchange.

In recent years, advances in semiconductor technology have led to the widespread use of electronic telephone exchange equipment, in which relay contacts and the like are made of semiconductors, from the viewpoint of miniaturization and high reliability. A well-known example of electronic relay contacts is the application of PNPN switches, which have low forward voltage drop, low on-resistance, can be separated from control circuits, and can easily be made to withstand high voltage.
A conventional circuit in which a so-called ringing signal sending circuit that uses a PNPN switch to ring a subscriber's telephone and monitor off-hook of the telephone is computerized is shown in FIG. 1, and the operation of each switch is shown in FIG.

In Figure 1, TEL is a subscriber telephone, S1
~S3 is a bidirectional PNPN switch with the anode and cathode sides of the PNPN switch connected in reverse, S4
~S8 is a one-way PNPN switch, S5~S8
This is a so-called reverse switch that reverses the polarity during response, etc. DET is a known ring trip circuit that monitors the subscriber's off-hook by the voltage of resistor R1, CR is a ringing signal source (75Vrms, 16Hz),
R ₁ and R ₂ are resistors, and BSA and BSB are battery side and earth side circuits of the communication current supply circuit, which are composed of transistors and the like.

Next, the operation will be explained. subscriber telephone
When there is an incoming call on the TEL and the telephone bell is to ring, as shown in Figure 2, a control circuit (not shown) drives switches S1 and S2, and the type of subscriber ringing signal (for example, in the case of a general incoming call) The bell rings for 1 second and stops for 2 seconds, commonly known as IR: 0.3 for special calls or police/fire calls.
Rings for seconds, stops for 0.2 seconds, rings for 0.3 seconds, stops for 2.2 seconds, commonly known as
Switches S3 and S4 are driven alternately in response to SIR (or continuous call, commonly known as CR). That is, while the switch S3 is being driven, the path is the ground air, the calling signal source CR, the switch S3, the resistor _R1 , the switch _S1 , the telephone TEL, the switch _S2 , the resistor _R2 , and the battery.
The bell of the telephone TEL rings with the call signal from the call signal source CR. Also, when the switch S3 is restored and the switch S4 is activated, the earth-air switch S4-
Stop the ringing of the bell along the path of resistance R ₁ (same as when the bell rings). The trip circuit DET is the current (voltage) that flows through the resistor R ₁ while the calling signal is being sent and when it is stopped.
The system monitors the subscriber's off-hook and outputs the result to a control circuit (not shown). In addition, Switch S5
-S8 are all turned off during the call control, and prevent the call signal from flowing into the call current supply circuits BSA and BSB.

When the subscriber goes off-hook, the trip circuit
Based on the output of DET, a control circuit (not shown) stops driving switches S1 to S4, and also drives switches S5 and S6. The supply circuit BSA--battery path supplies call current to the subscriber for incoming calls. The switches S7 and S8 are not involved in the incoming call operation, but when notifying the telephone TEL of the called subscriber's response at the time of outgoing call, as is well known, they operate in the following manner. That is, in response to the called subscriber's response, a control circuit (not shown) turns off switches S5 and S6, and since switches S5 and S6 are PNPN switches, it turns off call current supply circuits BSB and BSA, and temporarily cuts off the DC current. After that, the call current supply circuits BSA and BSB are turned on again, and the switches S7 and S8 are turned on to reverse the current flowing through the telephone set TEL.

In such a configuration, the following problems occur and need to be addressed.

(1) When operating from signal sending (S3 operation) to ground air sending (S4 operation) or vice versa, switches S3 and S4 are not PNPN switches even if the control circuit issues an ON (or OFF) driving instruction to each switch. As a result, switch S3 cannot be turned off due to the self-holding work of the PNPN switch until the ringing signal current becomes near zero, resulting in a state in which switches S3 and S4 are turned on simultaneously (short circuit), and switches S3 and S
4 is burnt out. Therefore, after switch S3 (or S4) is completely turned off, switch S4
(or S3) is turned on, so-called exclusive logic circuits must be added to switches S3 and S4.

(2) If a ground fault occurs on the switch S2 side line due to a subscriber line line fault while sending out a ringing signal, an excessive current will flow in the path from earth to switch S2 to resistor R ₂ to battery, and resistor R ₂ will burn out. Therefore, it is necessary to increase the resistance strength (increase the size) or add a ground fault detection circuit to the resistor _R2 and have a function to turn off the switch S2 upon ground fault detection. Switch S2 is normally a PNPN switch that does not have a current cutoff function, so it must be a special switch that has a cutoff function (for example, a known gate turn-off thyristor).
is required, and the number of elements also increases.

(3) When off-hook, DC flows through switches S1, S2, S3 (or S4), so S1 or S
The S2 switch is required to have a current cutoff function, and the S2 switch is special in relation to the previous item.

As mentioned above, it is difficult to digitize the signal sending circuit without complicating the switch itself and its peripheral circuits, and there are difficulties in making the circuit smaller and more economical. Furthermore, when converting to LSI, there was a limit to the degree of integration because the signals handled were high voltage (75Vrms), and increasing the number of elements meant increasing chip size, which was difficult to achieve economically.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a calling signal sending system that is economical and suitable for integrated circuit implementation.

The key point of the present invention is to utilize the reverse switch connected in parallel with the calling signal sending circuit and a part of the call current supply circuit during calling control, so that the switch's exclusive logic circuit, which is necessary for the calling signal sending circuit, can be used for calling control. This eliminates the need for disconnection functions, ground fault detection circuits, etc., reduces the number of elements, and allows the switch to be used as a normal switch.
The reason is that it can be configured with a PNPN switch.

The present invention will be explained in detail below with reference to the drawings. Third
The figure shows an embodiment of the present invention, and the same parts as in FIG. 1 are given the same symbols. First in terms of composition
There are two differences from the diagram in that switches S3 and S4 are removed and switch S2 is a one-way PNPN switch.

Next, the operation will be explained. The operation of each switch is shown in FIG. Since the outgoing operation is the same as in FIG. 1, the explanation will be omitted, and the incoming call operation will be explained. When there is an incoming call on the subscriber telephone TEL and the telephone bell is to ring, a control circuit (not shown) first drives the switch S8. Next, switches S1, S2 and switch S are activated depending on the type of subscriber calling signal.
Turn 7 on and off. That is, as shown in FIG. 4, when switches S1 and S2 are turned on when sending a ringing signal, during the half cycle period when the polarity of the ringing signal is positive due to the directionality of switches S2 and S8, the ringing signal source CR- is turned on. Resistor R ₁ - Switch S1 - Telephone TEL - Switch S8 - Battery side talk current supply circuit BSA Battery path, negative half cycle is battery - Resistor R ₂ - Switch S2 - Telephone TEL - Switch S1 - Resistor
_R1 - Signal source CR - Ring the telephone TEL bell on the path of earth air. During the ringing signal stop period, switches S1 and S2 are turned off and switch S7 is turned on, so that the path from earth to telephone current supply circuit BSB to switch S7 to telephone TEL to switch S8 to telephone current supply circuit BSA to battery is Monitor subscriber off-hook. That is, the off-hook monitoring of the subscriber is performed by using the ring trip circuit DET while the ringing signal is being sent.
During the suspension period, the call current supply circuits BSA and BSB
Let's do it.

As described above, according to the present invention, since the switch S8 is operated in the call control state, monitoring of ground faults can be realized by the communication current supply circuit BSA, and a special ground fault detection circuit is not required. Also, when switching the ringing signal, due to the self-holding characteristic of the PNPN switch, a collision (simultaneous ON) of switches S1 and S7 occurs, but the resistor _R1 and the call current supply circuit BSB
Since the current is limited by the internal resistance of the switch, there is no need to worry about the switch burning out, and there is no need for a special exclusive logic circuit. Furthermore, when a subscriber goes off-hook while a ringing signal is being sent, direct current flows through the switches S1 and S2, but if an off instruction is given to the switches S1 and S2 from a control circuit (not shown), the switch S1 will turn off during the negative polarity period of the ringing signal. , S2 temporarily becomes zero, so the current flowing through switch S2 is automatically restored.
2, the current cutting function is no longer required, the number of circuits and elements is reduced, and all switches can be configured with regular PNPN switches, and switches S3 and S4 are also no longer required, which is effective in making the device more compact and economical. be.

[Brief explanation of the drawing]

1 is a diagram showing a conventional circuit, FIG. 2 is an operation diagram of FIG. 1, FIG. 3 is a circuit diagram showing an embodiment of the calling signal sending method according to the present invention, and FIG. 4 is an operation diagram of FIG. It is a diagram. TEL: Telephone, DET: Ring trip circuit,
S1 to S8: PNPN switch, CR: calling signal source, BSA, BSB: talking current supply circuit, R ₁ , R ₂ :
resistance.

Claims (1)

[Claims] 1. A first switch connected between a first line of a subscriber line and a battery side circuit of a communication current supply circuit;
a second switch connected between a second line of the subscriber line and the earth side circuit of the talking current supply circuit; a first line of the subscriber line and the earth side circuit of the talking current supply circuit; and a fourth switch connected between the second line of the subscriber line and the battery side circuit of the talking current supply circuit, The switch No. 4 is a one-way semiconductor switch whose anode side is connected to the line side, and the third and fourth switches serve as reverse switches for the communication current to the subscriber line with respect to the first and second switches. a fifth switch connected to the first line of the subscriber line and comprising a bidirectional semiconductor switch; a fifth switch connected to the first line of the subscriber line in series with the fifth switch;
a ringing signal source connected to the second line of the subscriber line, and a sixth switch consisting of a one-way semiconductor switch connected in series with a battery to the second line of the subscriber line and having its cathode side connected to the line side. In preparation, during the call control, the first and second switches are turned off and the fourth switch is turned on, and during the call signal sending period during the call control,
The fifth and sixth switches are controlled to be turned on, the third switch is controlled to be turned off, and during the period during which ringing signal transmission is stopped during the ringing control, the fifth and sixth switches are controlled to be turned off; A calling signal sending method characterized by turning on a third switch.